linux-kernel - Re: [PATCH 1/1] apparmor: use SHASH_DESC_ON

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Message-ID: <dcab01f9-d751-a454-7b35-bc00e845b2d0@canonical.com>
Date:   Tue, 28 Mar 2017 15:02:47 -0700
From:   John Johansen <john.johansen@...onical.com>
To:     Nicolas Iooss <nicolas.iooss_linux@....org>,
        James Morris <james.l.morris@...cle.com>,
        "Serge E. Hallyn" <serge@...lyn.com>,
        linux-security-module@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/1] apparmor: use SHASH_DESC_ON_STACK

On 03/05/2017 06:30 AM, Nicolas Iooss wrote:
> When building the kernel with clang, the compiler fails to build
> security/apparmor/crypto.c with the following error:
> 
>     security/apparmor/crypto.c:36:8: error: fields must have a constant
>     size: 'variable length array in structure' extension will never be
>     supported
>                     char ctx[crypto_shash_descsize(apparmor_tfm)];
>                          ^
> 
> Since commit a0a77af14117 ("crypto: LLVMLinux: Add macro to remove use
> of VLAIS in crypto code"), include/crypto/hash.h defines
> SHASH_DESC_ON_STACK to work around this issue. Use it in aa_calc_hash()
> and aa_calc_profile_hash().
> 
> Signed-off-by: Nicolas Iooss <nicolas.iooss_linux@....org>
Acked-by: John Johansen <john.johansen@...onical.com>

I'll pull it into my tree and send it up this week


> ---
>  security/apparmor/crypto.c | 32 +++++++++++++-------------------
>  1 file changed, 13 insertions(+), 19 deletions(-)
> 
> diff --git a/security/apparmor/crypto.c b/security/apparmor/crypto.c
> index de8dc78b6144..136f2a047836 100644
> --- a/security/apparmor/crypto.c
> +++ b/security/apparmor/crypto.c
> @@ -31,10 +31,7 @@ unsigned int aa_hash_size(void)
>  
>  char *aa_calc_hash(void *data, size_t len)
>  {
> -	struct {
> -		struct shash_desc shash;
> -		char ctx[crypto_shash_descsize(apparmor_tfm)];
> -	} desc;
> +	SHASH_DESC_ON_STACK(desc, apparmor_tfm);
>  	char *hash = NULL;
>  	int error = -ENOMEM;
>  
> @@ -45,16 +42,16 @@ char *aa_calc_hash(void *data, size_t len)
>  	if (!hash)
>  		goto fail;
>  
> -	desc.shash.tfm = apparmor_tfm;
> -	desc.shash.flags = 0;
> +	desc->tfm = apparmor_tfm;
> +	desc->flags = 0;
>  
> -	error = crypto_shash_init(&desc.shash);
> +	error = crypto_shash_init(desc);
>  	if (error)
>  		goto fail;
> -	error = crypto_shash_update(&desc.shash, (u8 *) data, len);
> +	error = crypto_shash_update(desc, (u8 *) data, len);
>  	if (error)
>  		goto fail;
> -	error = crypto_shash_final(&desc.shash, hash);
> +	error = crypto_shash_final(desc, hash);
>  	if (error)
>  		goto fail;
>  
> @@ -69,10 +66,7 @@ char *aa_calc_hash(void *data, size_t len)
>  int aa_calc_profile_hash(struct aa_profile *profile, u32 version, void *start,
>  			 size_t len)
>  {
> -	struct {
> -		struct shash_desc shash;
> -		char ctx[crypto_shash_descsize(apparmor_tfm)];
> -	} desc;
> +	SHASH_DESC_ON_STACK(desc, apparmor_tfm);
>  	int error = -ENOMEM;
>  	__le32 le32_version = cpu_to_le32(version);
>  
> @@ -86,19 +80,19 @@ int aa_calc_profile_hash(struct aa_profile *profile, u32 version, void *start,
>  	if (!profile->hash)
>  		goto fail;
>  
> -	desc.shash.tfm = apparmor_tfm;
> -	desc.shash.flags = 0;
> +	desc->tfm = apparmor_tfm;
> +	desc->flags = 0;
>  
> -	error = crypto_shash_init(&desc.shash);
> +	error = crypto_shash_init(desc);
>  	if (error)
>  		goto fail;
> -	error = crypto_shash_update(&desc.shash, (u8 *) &le32_version, 4);
> +	error = crypto_shash_update(desc, (u8 *) &le32_version, 4);
>  	if (error)
>  		goto fail;
> -	error = crypto_shash_update(&desc.shash, (u8 *) start, len);
> +	error = crypto_shash_update(desc, (u8 *) start, len);
>  	if (error)
>  		goto fail;
> -	error = crypto_shash_final(&desc.shash, profile->hash);
> +	error = crypto_shash_final(desc, profile->hash);
>  	if (error)
>  		goto fail;
>  
>